Field of the Invention
The present invention relates to an optical scanning apparatus and an image forming apparatus including the optical scanning apparatus.
Description of the Related Art
In an electrophotographic image forming apparatus, a photoconductor (hereinafter referred to as a photoconductor drum for convenience) is irradiated with a light beam emitted from an optical scanning apparatus, so that a latent image is formed on the photoconductor drum. The latent image is developed and visualized by using toner, so that a toner image is formed. The toner image formed on the photoconductor drum is transferred onto a recording medium, and fixed to the recording medium by a fixing device which applies heat and pressure to the toner image. The recording medium on which an image is formed is discharged to the outside of the apparatus.
The optical scanning apparatus includes a light source, a rotating polygon mirror that is rotated to deflect a light beam emitted from the light source, and lenses and mirrors that guide the light beam deflected by the rotating polygon mirror to the photoconductor drum. These components are accommodated and retained in an optical box (housing). FIG. 9A is a schematic sectional view, taken along a plane that passes through the center of a leaf spring 1702a, illustrating a structure in which a commonly used optical component is retained. A reflection mirror 20, which is an optical component, is retained in an optical box 201 by a pressing force applied by the leaf spring 1702a, which is elastically deformable. In this structure, a first pressing portion 1705a presses a mirror edge portion 708, which have a low strength, of the reflection mirror 20. Therefore, there is a risk that the mirror edge portion 708 will be worn, chipped, or cracked. If powder or small pieces generated as a result of the mirror being worn, chipped, or cracked adhere to the mirror, the reflectance of the mirror decreases. As a result, the intensity of the light beam guided to the photoconductor drum will become lower than the desired intensity according to the design.
Japanese Patent Laid-Open No. 2010-237537, for example, proposes a structure for preventing the reflection mirror 20 from being worn, chipped, or cracked due to the leaf spring 1702a. In this structure, the leaf spring is inserted to a predetermined location while a holder portion is bent by an assembly jig such that a reflection-mirror-pressing portion of the leaf spring is compressed. Since the reactive force generated when the holder portion is bent is received by the assembly jig, the leaf spring may be prevented from coming into contact with the reflection mirror 20 in the process of attaching the leaf spring. Even when the leaf spring comes into contact with the reflection mirror 20, the reflection mirror 20 receives only a small pressing force. Therefore, the leaf spring may be attached without causing the mirror edge portion of the reflection mirror 20 to receive a force (or a stress) that causes wearing, chipping, or cracking thereof. A structure illustrated in FIG. 9B, for example, has also been proposed in which a first pressing portion 1705b of a leaf spring 1702b presses a mirror flat surface 710 instead of the mirror edge portion 708.
In the structure illustrated in FIG. 9B, the stress applied to the mirror edge portion 708 of the reflection mirror 20 in the state in which the leaf spring 1702b is attached is smaller than that in the structure illustrated in FIG. 9A. However, as illustrated in FIG. 9C, when the leaf spring 1702b is pressed downward to insert the leaf spring 1702b, owing to the reactive force of a third pressing portion 704 that presses a mirror reflective surface 706, the leaf spring 1702b is pressed in the direction of arrow 711 in FIG. 9C. Also, as illustrated in FIG. 9C, the leaf spring 1702b is tilted by a large amount due to an engagement portion 703. As a result, the leaf spring 1702b comes into contact with the mirror edge portion 708. To prevent the mirror edge portion 708 form being worn, chipped, or cracked, it is desirable to prevent the leaf spring 1702b and the mirror edge portion 708 from coming into contact with each other in a period from start to completion of the process of attaching the leaf spring 1702b. 